JP 2011-31365A describes that a cover is attached to a surface portion of a robot with a bolt. In case where a robot is used for manufacturing food or medicine, germicidal treatment is performed by washing the surface of the cover with medical fluid or water and then drying, or by exposing the surface of the cover to medicine gas.
In JP 2011-31365A, since the bolt is exposed from the surface of the cover, projection and recess is formed around the bolt. Medical fluid or water may easily remain at the projection and recess, or bacterial growth may be promoted at the projection and recess.